This invention relates to a method of sewing a buttonhole pattern and, more particularly, to an improved method for sewing such a pattern wherein the side bars are formed by sewing in the same direction to provide a uniform and esthetically pleasing appearance.
A conventional buttonhole pattern sewn by a conventional zig zag stitch household sewing machine includes two spaced-apart parallel rows of zig zag stitches, called side bars, joined at their ends by barring stitches of greater width and extending across both rows of side bar stitches. The separation between the rows of side bar stitches defines the cutting space of the buttonhole.
It the two rows of zig zag stitches forming the side bars of the buttonhole pattern are produced by first sewing one row of zig zag side bar stitches in a first direction and subsequently sewing the other row of zig zag side bar stitches in the opposite direction, it is found that the stitches sewn in the second direction tend to differ in spacing and regularity as compared with the stitches sewn in the first direction, thus producing a buttonhole which is unsatisfactory from an appearance point of view.
One prior method used to avoid the above-mentioned disadvantage is to reverse the work or material by 180.degree. upon completion of the first row of zig zag side bar stitches. This procedure is highly combursome and impractical in cases of relatively large work pieces or large sizes of sewing material.
Another prior method consists in lifting the presser foot upon completion of the first row of zig zag side bar stitches and pulling back the work to a position in line with and spaced laterally from the starting point, and then sewing a second row of zig zag stitches parallel to and in the same direction as the first row. This results in the final buttonhole having an obliquely extending cross-over thread from the end of the first row to the beginning of the second row due to the pulling back of the work, which is considered an impairment of the appearance of the buttonhole as well as causing other difficulties and defects.
Still another prior method is disclosed in U.S. Pat. No. 2,977,913, wherein a first row of zig zag stitches is sewn in one direction, a line of straight short stitches is sewn in the opposite direction in laterally spaced and parallel relationship to the first row, and then a second row of zig zag stitches is sewn in the same direction as the first row to overlie the line of straight short stitches. Depending upon the thread used, the row of zig zag stitches sewn over the line of straight short stitches may be visibly different from the simple row of zig zag stitches sewn without underlying straight stitches. The sewing machine operator must make many sewing machine adjustments to produce a simple buttonhole, changing from zig zag stitching to straight stitching and then back to zig zag stitching, which is time consuming and a burden on the operator. Also, because the controls of the sewing machine must be changed from a first zig zag stitch position to a second straight stitch position and then back to a third zig zag stitch position, the rows of zig zag stitches may not be uniform due to a slight difference in the setting of the zig zag stitch position between making the first row and second row of zig zag stitches.
Yet another prior method is disclosed in U.S. Pat. No. 3,570,433, wherein parallel rows of zig zag stitches are sewn in the same direction of feed, each row overlying a line of long stitches formed in the opposite direction of feed. This patent discloses a further method wherein parallel rows of zig zag stitches are sewn in the same direction of feed, one of the rows overlying a row of long zig zag stitches of the same width as the top row. The second of these methods results in a non-uniform appearance of the two side bars. The first of these methods does provide a uniform appearance of the side bars but each of the side bars is formed with a narrow ridge running down the center thereof.
It is therefore an object of the present invention to provide an improved method of forming a buttonhole pattern including a pair of parallel rows of zig zag stitches, whereby the above-mentioned and related difficulties and drawbacks are substantially avoided.
It is another object of this invention to provide an improved method of forming a buttonhole pattern including parallel rows of zig zag stitches where the individual rows are characterized both by an exact parallelism as well as by an equal structure and uniform appearance of the stitches.
It is yet another object of this invention to provide an improved method of forming a buttonhole pattern including parallel rows of zig zag stitches which is of increased strength.
It is still another object of this invention to provide an improved method of forming a buttonhole pattern including parallel rows of zig zag stitches wherein the side bars are crowned to provide an attractive appearance.